The present invention relates to a vane compressor for compressing a gas such as a refrigerant gas, and more particularly to an arrangement for adjusting back pressure acting on vanes in such a vane compressor.
Vane compressors have a compressor body composed generally of a pair of side blocks securely mounted on both sides of a cylinder. A rotor with a plurality of vanes fitted in slits defined therein is disposed in the compressor body, the vanes and the rotor jointly defining compression chambers in the compressor body. Rotation of the rotor causes distal ends of the vanes to slide against the inner peripheral surface of the cylinder, thereby enlarging and reducing the volumes of the compression chambers for compressing a gas therein. During operation of the vane compressor, it is necessary that the compression chambers be sealed by the distal ends of the vanes slidably pressed against the inner peripheral surface of the cylinder. To meet this requirement, the vanes are pushed radially outwardly under centrifugal forces acting thereon as well as by high-pressure oil supplied from an oil sump into back-pressure chambers defined between radially inward ends of the vanes and the vane slits in the rotor. In operation, the vanes will be retracted deeply into the vane slits when they move across a pump outlet defined in the cylinder against the back pressure on the vanes. After the vanes have moved past the pump outlet, they will be thrust out into hitting engagement with the inner peripheral surface of the cylinder, thus causing noise referred to as chattering.